﻿/* Copyright 2021-present MongoDB Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace MongoDB.Bson.TestHelpers
{
    // https://github.com/dotnet/samples/blob/main/csharp/parallel/ParallelExtensionsExtras/TaskSchedulers/ThreadPerTaskkScheduler.cs
    public sealed class ThreadPerTaskScheduler : TaskScheduler
    {
        /// <summary>Gets the tasks currently scheduled to this scheduler.</summary> 
        /// <remarks>This will always return an empty enumerable, as tasks are launched as soon as they're queued.</remarks> 
        protected override IEnumerable<Task> GetScheduledTasks() { return Enumerable.Empty<Task>(); }

        /// <summary>Starts a new thread to process the provided task.</summary> 
        /// <param name="task">The task to be executed.</param> 
        protected override void QueueTask(Task task)
        {
            new Thread(() => TryExecuteTask(task)) { IsBackground = true }.Start();
        }

        /// <summary>Runs the provided task on the current thread.</summary> 
        /// <param name="task">The task to be executed.</param> 
        /// <param name="taskWasPreviouslyQueued">Ignored.</param> 
        /// <returns>Whether the task could be executed on the current thread.</returns> 
        protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
        {
            return TryExecuteTask(task);
        }
    }
}
